<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div th:fragment="header" style="border: 1px solid red;">
        <span>ssssssssssssssssssssssss</span>
    </div>
</body>
</html>